Chapter 1 Chemical Foundations - PBworks

Chapter 1

Chemical Foundations

AP*

AP Learning Objectives

▪ LO 2.7 The student is able to explain how solutes can be separated by chromatography based on intermolecular interactions. (Sec 1.10)

▪ LO 2.10 The student can design and/or interpret the results of a separation experiment (filtration, paper chromatography, column chromatography, or distillation) in terms of the relative strength of interactions among and between the components. (Sec 1.10)

▪ LO 3.10 The student is able to evaluate the classification of a process as a physical change, chemical change, or ambiguous change based on both macroscopic observations and the distinction between rearrangement of covalent interactions and noncovalent interactions. (Sec 1.10)

Section 1.1 Chemistry: An OverviewSection 1.1 Chemistry: An Overview

▪ A main challenge of chemistry is to understand the connection between the macroscopic world that we experience and the microscopic world of atoms and molecules.

▪ You must learn to think on the atomic level.

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Atoms vs. Molecules

▪ Matter is composed of tiny particles called atoms. ▪ Atom: smallest part of an element that is still that element. ▪ Molecule: Two or more atoms joined and acting as a unit.

4


Oxygen and Hydrogen Molecules

• Use subscripts when more than one atom is in the molecule.

5


A Chemical Reaction

▪ One substance changes to another by reorganizing the way the atoms are attached to each other.

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Section 1.2 The Scientific Method

Science

▪ Science is a framework for gaining and organizing knowledge.

▪ Science is a plan of action — a procedure for processing and understanding certain types of information.

▪ Scientists are always challenging our current beliefs about science, asking questions, and experimenting to gain new knowledge.

▪ Scientific method is needed.

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Fundamental Steps of the Scientific Method

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• Process that lies at the center of scientific inquiry.


Scientific Models

• A summary of repeatable observed (measurable) behavior.

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Law

Theory (Model)

• Set of tested hypotheses that gives an overall explanation of some natural phenomenon.

Hypothesis

• A possible explanation for an observation.

Section 1.3 Units of Measurement

The Fundamental SI Units

Physical Quantity Name of Unit Abbreviation

Mass kilogram kg

Length meter m

Time second s

Temperature kelvin K

Electric current ampere A

Amount of substance mole mol

Luminous intensity candela cd

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Prefixes Used in the SI System

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• Prefixes are used to change the size of the unit.


Prefixes Used in the SI System

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Mass ≠ Weight

▪ Mass is a measure of the resistance of an object to a change in its state of motion. Mass does not vary. !

▪ Weight is the force that gravity exerts on an object. Weight varies with the strength of the gravitational field.

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Section 1.4 Uncertainty in Measurement

▪ A digit that must be estimated in a measurement is called uncertain.

▪ A measurement always has some degree of uncertainty. It is dependent on the precision of the measuring device.

▪ Record the certain digits and the first uncertain digit (the estimated number).

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Measurement of Volume Using a Buret

▪ The volume is read at the bottom of the liquid curve (meniscus).

▪ Meniscus of the liquid occurs at about 20.15 mL. ▪ Certain digits: 20.15 ▪ Uncertain digit: 20.15

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Precision and Accuracy

Accuracy

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• Agreement of a particular value with the true value.

Precision

• Degree of agreement among several measurements of the same quantity.


Precision and Accuracy

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Section 1.5 Significant Figures and Calculations

Rules for Counting Significant Figures

1. Nonzero integers always count as significant figures. ▪ 3456 has 4 sig figs (significant figures).

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2. There are three classes of zeros. a. Leading zeros are zeros that precede all the nonzero digits. These do not count as significant figures. ▪ 0.048 has 2 sig figs.

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b. Captive zeros are zeros between nonzero digits. These always count as significant figures. ▪ 16.07 has 4 sig figs.

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c. Trailing zeros are zeros at the right end of the number. They are significant only if the number contains a decimal point. ▪ 9.300 has 4 sig figs. ▪ 150 has 2 sig figs.

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3. Exact numbers have an infinite number of significant figures. ▪ 1 inch = 2.54 cm, exactly. ▪ 9 pencils (obtained by counting).

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Significant Figures in Mathematical Operations

1. For multiplication or division, the number of significant figures in the result is the same as the number in the least precise measurement used in the calculation. 1.342 × 5.5 = 7.381 ! 7.4

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Significant Figures in Mathematical Operations

2. For addition or subtraction, the result has the same number of decimal places as the least precise measurement used in the calculation.

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Corrected

23.4457.83

31.2831.275

+

!!!!→

Section 1.7 Dimensional Analysis

Example #1

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1 ft 12 in and 12 in 1 ft

A golfer putted a golf ball 6.8 ft across a green. How many inches does this represent?

• To convert from one unit to another, use the equivalence statement that relates the two units. !1 ft = 12 in

!The two unit factors are:


Example #1

▪ Derive the appropriate unit factor by looking at the direction of the required change (to cancel the unwanted units).

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6.8 ft12 in 1 ft

× = in


Example #1

▪ Multiply the quantity to be converted by the unit factor to give the quantity with the desired units.

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6.8 ft12 in 1 ft

× = 82 in


Example #2

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An iron sample has a mass of 4.50 lb. What is the mass of this sample in grams? (1 kg = 2.2046 lbs; 1 kg = 1000 g)

4.50 lbs1 kg

2.2046 lbs×

1000 g 1 kg

× 3= 2.04 10 g×


What data would you need to estimate the money

you would spend on gasoline to drive your car from New York to Los Angeles? Provide estimates of values and a sample calculation.

34

CONCEPT CHECK!

Section 1.8 Temperature

Three Systems for Measuring Temperature

▪ Fahrenheit ▪ Celsius ▪ Kelvin

35


The Three Major Temperature Scales


Converting Between Scales

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K= C + 273


At what temperature does °C = °F?

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EXERCISE!


▪ Since °C equals °F, they both should be the same value (designated as variable x).

▪ Use one of the conversion equations such as: !!!

▪ Substitute in the value of x for both TC and TF. Solve for x.

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( )C F5 C 32 F9 F

= −!

!!

T T

EXERCISE!


40

( )C F5 C 32 F9 F

= −!

!!

T T

( )5 C 32 F9 F

= −!

!!

x x

40

So 40 C = 40 F

= −

− ° − °

x

EXERCISE!

Section 1.9 Density

▪ Mass of substance per unit volume of the substance.

▪ Common units are g/cm3 or g/mL.

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massDensity = volume

Section 1.9 Density

Example #1

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317.8 gDensity =

2.35 cm

Density = 37.57 g/cm

A certain mineral has a mass of 17.8 g and a volume of 2.35 cm3. What is the density of this mineral?

Section 1.9 Density

Example #2

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What is the mass of a 49.6-mL sample of a liquid, which has a density of 0.85 g/mL?

0.85 g/mL = 49.6 mL

x

mass = = 42 gx

Section 1.10 Classification of Matter

AP Learning Objectives, Margin Notes and References

▪ Learning Objectives ▪ LO 2.7 The student is able to explain how solutes can be separated by chromatography based on

intermolecular interactions. ▪ LO 2.10 The student can design and/or interpret the results of a separation experiment (filtration,

paper chromatography, column chromatography, or distillation) in terms of the relative strength of interactions among and between the components.

▪ LO 3.10 The student is able to evaluate the classification of a process as a physical change, chemical change, or ambiguous change based on both macroscopic observations and the distinction between rearrangement of covalent interactions and noncovalent interactions.

▪ AP Margin Notes ▪ Solutions do not contain components large enough to scatter visible light. See Tyndall effect in Chapter

11. ▪ The components of a solution can be separated by distillation. ▪ The components of a solution are so small that they cannot be separated by filtration. ▪ Additional AP References ▪ LO 2.10 (see APEC Lab 5, "Thin-Layer Chromatography”) ▪ LO 3.10 (see APEC Lab 9, "Actions, Reactions, and Interactions”)


Matter

▪ Anything occupying space and having mass. ▪ Matter exists in three states. ▪ Solid ▪ Liquid ▪ Gas

45


The Three States of Water

46


Solid

▪ Rigid ▪ Has fixed volume and shape.

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Liquid

▪ Has definite volume but no specific shape. ▪ Assumes shape of container.

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Gas

▪ Has no fixed volume or shape. ▪ Takes on the shape and volume of its container.

51


Mixtures

▪ Have variable composition.

53

Homogeneous Mixture

Heterogeneous Mixture

▪ Having visibly indistinguishable parts; solution.

▪ Having visibly distinguishable parts.


The Organization of Matter

59


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! Active Learning QuestionsThese questions are designed to be used by groups of students inclass.

1. a. There are 365 days per year, 24 hours per day, 12 months peryear, and 60 minutes per hour. Use these data to determinehow many minutes are in a month.

b. Now use the following data to calculate the number of min-utes in a month: 24 hours per day, 60 minutes per hour, 7 daysper week, and 4 weeks per month.

c. Why are these answers different? Which (if any) is more cor-rect? Why?

2. You go to a convenience store to buy candy and find the ownerto be rather odd. He allows you to buy pieces in multiples of four,and to buy four, you need $0.23. He only allows you to do thisby using 3 pennies and 2 dimes. You have a bunch of pennies anddimes, and instead of counting them, you decide to weigh them.You have 636.3 g of pennies, and each penny weighs 3.03 g. Eachdime weighs 2.29 g. Each piece of candy weighs 10.23 g.a. How many pennies do you have?b. How many dimes do you need to buy as much candy as pos-

sible?c. How much should all these dimes weigh?d. How many pieces of candy could you buy? (number of dimes

from part b)e. How much would this candy weigh?f. How many pieces of candy could you buy with twice as many

dimes?

3. When a marble is dropped into a beaker of water, it sinks to thebottom. Which of the following is the best explanation?a. The surface area of the marble is not large enough to be held

up by the surface tension of the water.b. The mass of the marble is greater than that of the water.c. The marble weighs more than an equivalent volume of the

water.d. The force from dropping the marble breaks the surface ten-

sion of the water.e. The marble has greater mass and volume than the water.Justify your choice, and for choices you did not pick, explainwhat is wrong about them.

4. You have two beakers, one filled to the 100-mL mark with sugar(the sugar has a mass of 180.0 g) and the other filled to the100-mL mark with water (the water has a mass of 100.0 g). Youpour all the sugar and all the water together in a bigger beakerand stir until the sugar is completely dissolved.a. Which of the following is true about the mass of the solu-

tion? Explain.i. It is much greater than 280.0 g.

ii. It is somewhat greater than 280.0 g.iii. It is exactly 280.0 g.iv. It is somewhat less than 280.0 g.v. It is much less than 280.0 g.

b. Which of the following is true about the volume of the solu-tion? Explain.

i. It is much greater than 200.0 mL.ii. It is somewhat greater than 200.0 mL.

iii. It is exactly 200.0 mL.iv. It is somewhat less than 200.0 mL.v. It is much less than 200.0 mL.

5. You may have noticed that when water boils, you can see bub-bles that rise to the surface of the water.a. What is inside these bubbles?

i. airii. hydrogen and oxygen gas

iii. oxygen gasiv. water vaporv. carbon dioxide gas

b. Is the boiling of water a chemical or physical change? Ex-plain.

6. If you place a glass rod over a burning candle, the glass appearsto turn black. What is happening to each of the following (phys-ical change, chemical change, both, or neither) as the candleburns? Explain each answer.a. the wax b. the wick c. the glass rod

7. Which characteristics of a solid, a liquid, and a gas are exhib-ited by each of the following substances? How would you clas-sify each substance?a. a bowl of pudding b. a bucketful of sand

8. You have water in each graduated cylinder shown:

1mL

0.5

5

4

mL

2

1

3

You then add both samples to a beaker. How would you writethe number describing the total volume? What limits the preci-sion of this number?

9. Paracelsus, a sixteenth-century alchemist and healer, adopted ashis slogan: “The patients are your textbook, the sickbed is yourstudy.” Is this view consistent with using the scientific method?

10. What is wrong with the following statement?“The results of the experiment do not agree with the theory.Something must be wrong with the experiment.”

11. Why is it incorrect to say that the results of a measurement wereaccurate but not precise?

12. What data would you need to estimate the money you wouldspend on gasoline to drive your car from New York to Chicago?Provide estimates of values and a sample calculation.

1047810_ch01_001-038.qxd 9/8/08 10:22 AM Page 31

Copyright 2010 Cengage Learning, Inc. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.

31

! Active Learning QuestionsThese questions are designed to be used by groups of students inclass.

1. a. There are 365 days per year, 24 hours per day, 12 months peryear, and 60 minutes per hour. Use these data to determinehow many minutes are in a month.

b. Now use the following data to calculate the number of min-utes in a month: 24 hours per day, 60 minutes per hour, 7 daysper week, and 4 weeks per month.

c. Why are these answers different? Which (if any) is more cor-rect? Why?

2. You go to a convenience store to buy candy and find the ownerto be rather odd. He allows you to buy pieces in multiples of four,and to buy four, you need $0.23. He only allows you to do thisby using 3 pennies and 2 dimes. You have a bunch of pennies anddimes, and instead of counting them, you decide to weigh them.You have 636.3 g of pennies, and each penny weighs 3.03 g. Eachdime weighs 2.29 g. Each piece of candy weighs 10.23 g.a. How many pennies do you have?b. How many dimes do you need to buy as much candy as pos-

sible?c. How much should all these dimes weigh?d. How many pieces of candy could you buy? (number of dimes

from part b)e. How much would this candy weigh?f. How many pieces of candy could you buy with twice as many

dimes?

3. When a marble is dropped into a beaker of water, it sinks to thebottom. Which of the following is the best explanation?a. The surface area of the marble is not large enough to be held

up by the surface tension of the water.b. The mass of the marble is greater than that of the water.c. The marble weighs more than an equivalent volume of the

water.d. The force from dropping the marble breaks the surface ten-

sion of the water.e. The marble has greater mass and volume than the water.Justify your choice, and for choices you did not pick, explainwhat is wrong about them.

4. You have two beakers, one filled to the 100-mL mark with sugar(the sugar has a mass of 180.0 g) and the other filled to the100-mL mark with water (the water has a mass of 100.0 g). Youpour all the sugar and all the water together in a bigger beakerand stir until the sugar is completely dissolved.a. Which of the following is true about the mass of the solu-

tion? Explain.i. It is much greater than 280.0 g.

ii. It is somewhat greater than 280.0 g.iii. It is exactly 280.0 g.iv. It is somewhat less than 280.0 g.v. It is much less than 280.0 g.

b. Which of the following is true about the volume of the solu-tion? Explain.

i. It is much greater than 200.0 mL.ii. It is somewhat greater than 200.0 mL.

iii. It is exactly 200.0 mL.iv. It is somewhat less than 200.0 mL.v. It is much less than 200.0 mL.

5. You may have noticed that when water boils, you can see bub-bles that rise to the surface of the water.a. What is inside these bubbles?

i. airii. hydrogen and oxygen gas

iii. oxygen gasiv. water vaporv. carbon dioxide gas

b. Is the boiling of water a chemical or physical change? Ex-plain.

6. If you place a glass rod over a burning candle, the glass appearsto turn black. What is happening to each of the following (phys-ical change, chemical change, both, or neither) as the candleburns? Explain each answer.a. the wax b. the wick c. the glass rod

7. Which characteristics of a solid, a liquid, and a gas are exhib-ited by each of the following substances? How would you clas-sify each substance?a. a bowl of pudding b. a bucketful of sand

8. You have water in each graduated cylinder shown:

1mL

0.5

5

4

mL

2

1

3

You then add both samples to a beaker. How would you writethe number describing the total volume? What limits the preci-sion of this number?

9. Paracelsus, a sixteenth-century alchemist and healer, adopted ashis slogan: “The patients are your textbook, the sickbed is yourstudy.” Is this view consistent with using the scientific method?

10. What is wrong with the following statement?“The results of the experiment do not agree with the theory.Something must be wrong with the experiment.”

11. Why is it incorrect to say that the results of a measurement wereaccurate but not precise?

12. What data would you need to estimate the money you wouldspend on gasoline to drive your car from New York to Chicago?Provide estimates of values and a sample calculation.

1047810_ch01_001-038.qxd 9/8/08 10:22 AM Page 31

Copyright 2010 Cengage Learning, Inc. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.


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Chapter 1 Chemical Foundations - PBworks

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